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94 454 ¾ sub Surging at night only !! update !!

W

WakeBoard&4X4er

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Last night I was driving my 94 sub home with a trailer for the first time, when I noticed some things. At 70 mph the truck would surge some? I looked that the temp and it was ok, but the volts were down in the 11.5-12.5 range, is that normal? I have been noticed that when I drive with the AC in the day the same problem. I was thinking I would find out what the deal is before I take off with my blazer on the trailer.

This is what I am thinking,
1. alternator is going bad.
2. new Fuel Filter.
3. know it needs a new belt.
4. Friend thinks it my be the battery.

What I think I might do is pull the battery from the blazer and put it in the sub and change the belt. It that does not fix, new fuel filter. Last new alternator. If that does not do it I will take to a shop.

What do you all think???
 
Re: 94 454 ¾ sub Surging at night only

If you haven't changed the fuel filter in a while, I'd do that anyway. Same with the belt. As far as the alt & battery, just take it to a local Checker/Auto Zone and have em both checked. That's easier, cheaper, and will give you a difinative answer on if they are good or not. After that, reevaluate & get an answer from someone much less mechanically challenged than myself /forums/images/graemlins/grin.gif
 
Re: 94 454 ¾ sub Surging at night only

Sounds like your alternator is near death. Anytime that you have a high current load on it (running at night with lights, or in the daytime with the a/c blower(s) on high) your voltage is dropping. The alternator should be able to maintain 13.8 volts while every gadget on the truck is going full blast. The battery is simply a voltage storage device, it's the alternator that "fills it up". When you're seeing the 11.5 volt readings, the battery is being discharged because the alternator isn't doing it's part. /forums/images/graemlins/frown.gif

Our '94 Sub maintains 13.8 volts with the a/c on, both the front and rear fans going full blast, the headlights on, wipers running, and the radio playing. /forums/images/graemlins/cool.gif
 
Re: 94 454 ¾ sub Surging at night only

I'd agree with Harry. Sounds like the alternator is headed South. Mine did that last year-- a couple of goofy days, then BAM, it went to 12V. I was only a couple of miles from home, so I turned around and swapped with the Jeep for the day...

The good news is that a rebuilt alternator only cost me $43 at an auto electric shop. /forums/images/graemlins/cool.gif
 
Re: 94 454 ¾ sub Surging at night only

[ QUOTE ]
Sounds like your alternator is near death. Anytime that you have a high current load on it (running at night with lights, or in the daytime with the a/c blower(s) on high) your voltage is dropping. The alternator should be able to maintain 13.8 volts while every gadget on the truck is going full blast. The battery is simply a voltage storage device, it's the alternator that "fills it up". When you're seeing the 11.5 volt readings, the battery is being discharged because the alternator isn't doing it's part. /forums/images/graemlins/frown.gif

Our '94 Sub maintains 13.8 volts with the a/c on, both the front and rear fans going full blast, the headlights on, wipers running, and the radio playing. /forums/images/graemlins/cool.gif

[/ QUOTE ]

another culprit that doesn't get enough love, is the main power split off junction block on the firewall. I dunno if the newer burbs have one or not, but in the case of my older 77, one of the nuts that holds the main power cable on the breakout block was lose, and as such, making minimal contact, and not allowing a proper ammount of power to get from the alternator to anything important like the batteries, the power regulator, the ignition system, or for that matter, anything else on the truck.

good luck with it,

-The Ddragggon
 
Re: 94 454 ¾ sub Surging at night only

Yep...Alternator. Mine crapped out a couple weeks ago and was doing the same thing. It's probably making enough voltage...the rectifyer is taking a crap and it's going A/C. DC gages reading A/C voltage will read low. DC motors will run slow. Plays hell with the computer. My truck started poping fuses and the CB got radio noise in it when it happend.
 
Re: 94 454 ¾ sub Surging at night only

[ QUOTE ]
the main power split off junction block on the firewall. I dunno if the newer burbs have one or not,

[/ QUOTE ]
Yep, the newer trucks have a massive one. It has 4 or 5 posts (very nice for doing "upgrades" on older trucks). /forums/images/graemlins/cool.gif It's hiding under the black plastic cover on the firewall that also houses the fuel pump relay. /forums/images/graemlins/thumb.gif
 
Re: 94 454 ¾ sub Surging at night only

Hey Rich

This sounds pretty interesting as it's something I've overlooked in squaring my electical system up. I wonder if you have a pic of this guy (main power split off junction block)? I dont have a shop manual yet - just working with Chilton & Haynes for the moment and they dont seem to list this. I suppose I could go out to the /forums/images/graemlins/burb.gif and start tracing wires from the battery & alternator, but it would be easier if I knew what I was looking for /forums/images/graemlins/wink.gif.

Ben
 
Re: 94 454 ¾ sub Surging at night only

When to Auto Zone and they put my Sub on some computer and it told me that when i was at 2000 i was putting out 13.5 Volts, but at idle i was at 11.2. what do you all make of this?

Big Block with o/d 3.73 and 30ish tires, i would think at 65 i would not be in the 2000 rpm range, but...

what should i look at now?
 
Re: 94 454 ¾ sub Surging at night only

Did they put a load on it? They need to load the system down, so that the alternator has to work hard to keep up with the demands. And it still should have been able to keep the voltage very close to 13.8 volts at idle.
 
Re: 94 454 ¾ sub Surging at night only

is that so. i do not trust the people at part stores that much, the best store i have heard was of backyard asking about spring bushing at telling them that they are waring out fast, and told him it was because he had a bodylift.

/forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rotfl.gif
 
Re: 94 454 ¾ sub Surging at night only

OK, I just came back in from the driveway... I fired up the Sub, turned on the headlights, the radio, front a/c on high, rear a/c on high, and even left the door open so all of the interior lights were also on. With the engine idling, my digital voltmeter showed 13.97 volts at the battery. /forums/images/graemlins/cool.gif So it sounds like it's time for you to get an alternator that works properly. /forums/images/graemlins/wink.gif
 
Re: 94 454 ¾ sub Surging at night only

if it was only putting out 11 at idle on his computer, he should have known your alternator was screwed. hopefully the newer suburban's alternator is up in an easy to access location, like my old skool sub's.

-Ddragggon
 
Re: 94 454 ¾ sub Surging at night only

yes it was Easy, up top, remove the S belt, 3 bolts 1 pug one nut. i would have taken about 15 mins if the parts store would have gave me the right belt! they one they gave me was about 1 inch to short! /forums/images/graemlins/angryfire.gif
so i had to drive back there and get the right part. /forums/images/graemlins/rolleyes.gif

runs better, i think i am going to change the fuel filter asap, but runs about 70% better.
 
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